Tutorial: Half-Square Triangles (HST)

To create half-square triangle (HST) units, we start with two squares that are 1″ larger than the finished size of the HST needed.

Cut two squares of scrap fabric at 5″ exactly (use two different prints). This will yield two HSTs with an unfinished size of 4.5″ or 4″ finished once completely sewn into the quilt block.

On the wrong side of one of the squares, with a pencil or other marking tool, mark a diagonal line, corner to corner.

From this drawn line, you’re going to stitch 1/4″ away on both sides. However, I prefer to draw my stitching lines on my fabric as well. I have this very hand tool, Quilter’s Quick Quarter that makes this easy.

Line up the middle of the tool, with the corners of my fabric square and draw the 1/4″ lines on both sides. You can use a regular ruler to achieve the same thing too.

Depending on which method you chose above, stitch 1/4″ away from the centre line, or on the drawn lines if you chose to draw the 1/4″ lines as I did. I use a couple of pins to keep the block from shifting. When I stitch on the drawn line, I like to use an open foot so that I can see exactly where I’m sewing.

This is what you’ll have. It’s normal for your block to be a little wavy as we’ve just sewn on the bias. Give it a good press to set the seams and flatten the block.

Cut in half directly on the diagonal line to yield two half-square triangle units.

If the fabrics you’ve chosen have a distinct light and dark, press towards the dark side. With the fabric you want to press towards on top, open up your HST and lightly finger press making sure there are no tucks at the corner edges. Be careful as this is a bias edge and you don’t want to distort it out of shape by pressing too hard. Press with your iron.

Take your HST block back to the cutting mat to trim. You’ll need a ruler with a 45 degree line on it. I really like the Easy Square Jr. Ruler for this as the lines are very easy to read.

Align the diagonal line (45 degrees) on the ruler with the diagonal on your block. Trim the block to exactly 4.5″. Trim a bit off both sides (top and right, if right-handed), turn the block around, and clean up the other two sides making sure to align the diagonal line and the block’s edge at the correct cutting size.

Remember that old saying, measure twice, cut once. Make sure you are reading your ruler correctly to trim to 4.5″

Download Free Tutorial

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Disclaimer: This free tutorial and all photos are copyright Michele Foster of Mishka’s Playground. I would be happy for you to share a link to this tutorial and one photo on your own blog. However, please do not copy the entire tutorial for free or for sale, and republish it as your own anywhere. Instead link back to this page for the instructions. Thank you for respecting my copyright and the amount of time and effort that has gone into creating this free tutorial.